Embodiments relate to an electrostatic discharge (ESD) voltage resistive current modeling method of an ESD protection device.
If electronic components used in a communication device are exposed to an ESD phenomenon, their internal circuits may be damaged or rendered unstable during operation. In relation to the ESD phenomenon, when an electronic device contacts a charge transferable object, static electricity is discharged to affect its internal circuit. For example, when a human body contacts an antenna or an external connection part of a communication device, the ESD phenomenon may occur.
To protect internal circuits from the ESD phenomenon, an electronic circuit is equipped with an ESD protection device. The ESD protection device may include a diode and be formed using a semiconductor fabrication process.
FIG. 1 is a plan view illustrating a structure of an ESD protection device. FIG. 2 is a graph illustrating an ESD current characteristic as a function of the voltage applied to an ESD protection device.
The ESD protection device 10 of FIG. 1 is a diode including an N-type diffusion layer 11, a junction layer 12, a P-type diffusion layer 13, and a contact electrode 14. The N-type diffusion layer 11 operates as an anode and the P-type diffusion layer 13 operates as a cathode.
For an the anode (i.e., N-type diffusion layer) 11 of the ESD protection device 10 having a length “a” of 30 μm and a width “b” of 10 μm, the ESD current as a function of voltage) is as shown in FIG. 2 for a given fabrication process.
In FIG. 2, the y-axis (vertical axis) represents the current through the ESD device at various voltages, in amperes (A). A first x-axis (horizontal axis, below the graph) represents the voltage V applied to a diode, and a second x-axis (above the graph) represents the current through the ESD device on a logarithmic scale.
In FIG. 2, measurement line c indicates a current of the anode 11 based on the voltage applied to the diode, and measurement line d indicates an amount of a leakage current based on the voltage applied to the diode.
Referring to FIG. 2, the measurement lines c and d infinitely increase beyond the measurement range (e.g., above point e). An ESD current at the point e is about 126 mA, and this means that the diode begins to breakdown at the point e. Accordingly, the above ESD current (e.g., at point e) at a voltage that the ESD device can withstand (e.g., the “withstanding voltage”) can be regarded as a breakdown current.
Based on this measurement result, the unit circumference of the anode 11 (i.e., the N-type diffusion layer) in the ESD protection device 10 can be calculated using Equation 1 below.ESD breakdown current per anode unit circumference=Iesd÷circumference of anode  [Equation 1]where Iesd represents an ESD current at the withstanding voltage, and the circumference of anode is (a+b)×2 (where a and b are as shown in FIG. 1).
Accordingly, if the ESD breakdown current (i.e., at the withstanding voltage) is 126 mA and the circumference of the anode 11 is 80 μm, the ESD breakdown current per anode unit circumference is 1.575 mA/μm.
Since this calculated ESD breakdown current depends on a first order function for the anode circumference, a linear relationship of an ESD breakdown current characteristic with respect to a diode area cannot be accurately expressed. Therefore, its accuracy can be improved.
For example, if a plurality of diodes are combined and used as one diode, they have the same ESD breakdown current characteristic as one diode having the same anode area as the plurality of diodes. However, an ESD breakdown current calculated using the first order function for circumference in Equation 1 has a different result. That is, if two diodes have the same area but different circumferences, or have the same circumference but different areas, it is difficult to normalize the ESD breakdown current characteristics. For this reason, when the ESD protection device is designed, it is typically designed larger than actually required in order to allow for errors in the ESD breakdown current. This reduces area efficiency of a design.